#pip {
    position: relative;
    height: 100%;
    width: 100%;
}

.content {
    position: absolute;
    left: 0;
    top: 0;
}

.content>img {
    max-width: 100%;
    min-width: 100%;
    position: absolute;
    left: 0;
    top: 0;
}

.mask {
    width: 100%;
    height: 100%;
    position: absolute;
    left: 0;
    top: 0;
    background: yellow;
}